The use of blister packs to hold medicaments for inhalation devices, for example in bronchodilation therapy, is well known. The blister packs usually consist of a base sheet in which blisters are formed. The blisters are arranged on the base sheet and can be filled with medicament to be administered through use of an inhalation device. A lid sheet is applied to cover the filled blisters and the two sheets are sealed together to form a blister pack.
There can, however, be problems associated with methods of filling the blisters with medicament. Powder, particularly the drug component of the powder, can tend to be attracted to the base sheet surface rather than to the blister pockets. This attraction of the drug to the base sheet can result in inaccurate filling of the blisters, create mess and potentially cause problems with adherence of the lid sheet to the base sheet. Such filling methods may also require a large reservoir of powder, potentially resulting in waste of the medicament.
The Applicants have now found that the potential problem of powder adherence can be overcome by using a filling method utilising a perforated plate to mask the base sheet surface during filling to avoid covering this area with powder. The perforated plate is simply moved into contact with the appropriate areas of the blister strip during filling and then moved away at the end of the method and can be reused in each cycle. This filling method, therefore, aims to prevent the powder adhering to the blister strip, rather than relying on using methods such as additional cleaning steps to remove the powder after it has accumulated. The filling method can also be used to fill other types of containers e.g. injection moulded plastic pockets, capsules or bulk containers.
The perforated plate is also used to assist with ensuring the correct dose of powder is loaded into the blind cavity. In one aspect, adjusting the size of the perforation enables different doses to be loaded into the blisters.
Another problem associated with filling blister packs with powdered medicament is that the powder often has poor flow properties, making accurate filling difficult. The applicants have found that this problem can be overcome by the use of a director, for example a blade, which can direct the powder into the perforations. The blade can be passed through the powder several times or multiple blades may be used to ensure that filling is accurate.
The applicants have also found that the method and apparatus described herein can also be used to form tablets by applying increased compaction forces to the powder. The use of this method avoids many of the pre-processing steps (e.g. granulation) usually involved in tablet formation by gravity feed of the powder.